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Leafcutter ants use prehensile legs to help chop up leaves

Leafcutter ants (Atta cephalotes) are farmers, collecting vast quantities of plant matter to fertilize the underground fungus crop on which they feed. New research shows that their legs are prehensile, allowing them to process leaves precisely and efficiently. Scientists filmed the insects as they collected and processed leaves in a laboratory nest. They identified 10 tasks performed by the ants to turn leaves into fungus food, from cutting and puncturing, to gently rocking finished leaf fragments into the network of fungal filaments. These delicate maneuvers are possible because the ants’ legs are prehensile, the team reports online today in the Royal Society Open Science. They use the flexible, multijointed tips to carefully grasp and manipulate fragments (see video, above). The researchers calculated that processing 1 square meter of fresh leaves into digestible fragments for the fungus requires about 3 km of cutting, equivalent to 1 million ant body lengths. Cutting leaves is hard work, and the ants may be living close to the limit of their energy budget, the authors say. Consistent with this, they found that the ants preferred smaller leaves, which they fed to the fungus as fragments, rather than pulverizing them into leaf pulp, as previously described, minimizing their work. The team says the ants displayed an unexpected diversity of leaf-processing behaviors, showing leafcutters as skilled crafters rather than mindless automatons.